LBZ / Allison - Cracking, snapping, popping, ticking sound???

[Quack_Addict]

The truck is a 2006 2500HD with LBZ Duramax and 6-speed Allison, <19,000 miles. The drivetrain has been making what I would describe as a chorus of LOUD cracking, snapping, popping and ticking sounds during cold and warm starts when the ambient temperature is about 65*F and higher. It doesn't make the noise every cold / warm start but it does it on a fairly regular basis. The noise is almost a certainty during hot ambient temperature starts (80's & hotter) when the engine is cool or warm.

As the engine comes up to temperature, the noise seems to dissipate and eventually go away, most of the time. There have been several instances though that the noise took about 10 miles to dissipate - it's obvious and loud enough that people's heads turn at stop lights.

There really doesn't seem to be any rhyme or reason to the noise other than it is there at idle, both in gear and in park. The noise is still there off-idle but you reach a point where engine noise overtakes the noise as you are pedaling the accelerator. The noise is coming somewhere from the powertrain or something that is connected to it - the noise seems to emanate most from the underside of the truck and the wheel wells. I have had the hood up a couple times when it was making the noise and it doesn't seem to be a top end noise - it is much more obvious through the wheel wells and truck's underside.

I can not say there a correlation to engine speed - sometimes the engine will be idling and you hear a random "tick" thrown in about once every second. Other times you hear a "tick, tick, tick" at a much more frequent interval that seems rythmic to engine speed. Other times, it's a louder cracking / popping sound - almost like a hot exhaust - but much louder and much crisper. Shut the engine off, no more noise.

The only thing I have ever heard make a noise like this in a vehicle is a cracked flex plate, but the truck has done this almost since day 1. By the time I get the truck to the dealer when it is making the noise, the engine has warmed up enough where it's quiet. Finally, on an unrelated service call, a Technician heard "a noise" but the noise dissipated before they could find the source - then they couldn't duplicate it.

Any ideas what this noise could be? It has not proven to be a functional issue yet, but the fact that the noise is there on such a regular and frequent basis is keeping me from having my peace of mind.

Thanks!

[EdHale]

Mine does a similar thing at start up. I her a crackingpopping metallic noise mostly from the drivers side. After a few minutes it goes away and never is noticeable other than right at the side of the truck. While in the cab with the door closed you can't hear it at all. It seems to come from under the driver's seat.
Ed

[More Power]

Take the serpentine belt off to see whether the sound is being produced by any of the engine driven accessories. The water pump is gear driven, so other than the alternator not alternating, you should be fine for the few minutes it might take to eliminate the accessories.

If it does it while sitting still, it's likely not the transmission, transfer case or drivelines. The flexplate and TC might be, but...

Jim

[Duramaster]

If this is the same noise that most all DMAX trucks have, it sounds to me like what you are hearing can also be described as a sound like a loose spark plug wire creating a "SNAP" sound. This is a known condition that has been around since the 2001 LB7's were out. The noise sounds like a mechanical typewriter. The last explanation of this from GM TAC was that it is caused by the thrust of the camshaft (end play). Another time it was thought to be cavatation in the oil. There used to be a bulletin for this. Basically a letter stating all is good and no engine damage is being done nor will there be any long term effects. I tried to locate the bulletin, but I am having no luck. I will post it here if I find it. ;)

[DmaxMaverick]

^

Bulletin No.: 02-06-01-022F (last updated 11-30-06)

If the noise sounds like a mechanical typewriter, that's probably it, and it's normal. It'll decrease with time and miles.

[More Power]

GM decreased the engine oil pressure in the LLY and LBZ engines below that produced by the LB7. The odd snapping (produced by the earlier LB7) didn't seem to be an issue with the newer engines - at least people stopped talking about it.

To me, the snapping sound produced by the LB7 was more like a loose flat washer intermittently rattling/ticking inside the driver's side aluminum intercooler tube. I felt then (and still do) that the sound was due to new oil gassing-off and creating gas bubbles that were compressed/popped in the engine's main/rod bearings. I always heard the sound right after an oil change and for about the next couple hundred miles - then not again till the oil was changed.

Jim

[gophergunner]

i always thought it was metal parts expanding as it warmed up........

similar to the sound you hear from ducts in the house when the furnace kicks on maybe......:confused:

just my thought but i'm not sure

[DieselMonk]

Not sure what you are talking about the snap, pop, cracling sound, but I sure do know what you are talking about that ticking sound. There is a bulleting out for it, but GM says do not fix and it is normal. Mine is ticking too, sounds like some one using a mechanical type writer with one finger. Sounds worse on the drivers side wheel housing, when it's warm outside and the truck hasn't reached op temperature. However, it shouldn't effect anything, besides making noise.

[EdHale]

As I said earlier, mine does this too, but only while it is coming up to operating temp. Then it is quiet. Did anyone actually say what it is? If so, I guess I missed it. Ed

[hapaschold]

what kinda oil ya using ? i ve been using 15w40.....mobile delav mostly,

slight noise when oil is new but after few hundred miles, ticking noise is gone,

my 02 dmax was another story....lots of ticking till the oil was diluted with diesel when the injectors went bad......

i notice on the lbz, the oil pressure is much less than the 02.......when approaching 5 k on oil it s way down on the pressure gauge at idle.......

[mark45678]

I have had 3 duramax trucks , every one of them has had the oil cavitation cracking/poping sound if they have fairly new oil in them. I use Rotella 15-40 , the issue seams ot go away as the oil ages some . my 2001 was the loudest and had the highest oil pressure. 27 min hot and 60+ at road speed hot. the LLY truck had slightly less oil pressure but still did it and my LBZ has less of a issue but it still does it if the oil has less then 2000~3000 miles on it.

[DieselMonk]

I don't see or hear any difference if the oil is new or 7000km on it. Ticks the same to me. It is only doing that during warm up, never during Op temp.

[NutNbutGMC]

...
my 02 dmax was another story....lots of ticking till the oil was diluted with diesel when the injectors went bad.........LMAO... Been there.

[bassomatic]

Any further ideas on this noise?? Any one know for sure what it is?
My 2004 is doing it now at 105,000 miles. Sometimes it gets so loud that I think the truck is about to explode. Comes and goes, sometimes happens for 5 minutes sometimes 30 minutes then I can go a week without hearing it. Several times I have had to pull over and shut down for awhile in the hopes that I can get home.
Going in for service on Wednesday. See what they say.

[Sea-Air-Ahh-LBZ]

I had a 91 Ford F150 a long time ago that made the exact same sounds that you described. It drove me nuts! Finally one day when my drive shaft fell off when I put it in reverse (the front end of the shaft next to the transmission) I saw that the needle bearings inside of the universal joints were TOASTED at both ends of the driveshaft. I took it to a drive shaft specialty shop and had both "U" joints replaced with "U" joints that had zerk fittings so they could be occasionally lubricated. END OF STRANGE SOUNDS END OF STORY. This might be your problem or NOT .. Something to ponder. I have a 07 GMC LBZ now with 20K miles and have not heard any of these type of sounds yet but if I do I am lookin at the U joints first.

[DIESEL5]

I was getting a similiar noise on my 06' but only at Gear changes ya know from park to drive and reverse and park again and also when i would pull away from a stop. I took it to the dealer and they found that indeed i had bad u-joints so they replaced the entire driveshaft and i have not had any noise since